This invention relates to an improved process for the production of higher hydrocarbons from lower olefins. More particularly, the invention relates to a process for producing higher hydrocarbons from a lower olefin feedstock also containing a contaminant such as butadiene which tends to deactivate oligomerization catalysts.
Converting lower olefins, such as ethylene, propylene, butylene and mixtures thereof, to higher hydrocarbons has been widely used, for example, to produce polymer gasoline. Recently, some work has been directed toward olefin oligomerization to produce higher hydrocarbons from lower olefins derived from methane conversion. See U.S. Pat. No. 4,556,749; and commonly assigned U.S. patent application Ser. Nos. 06/728,060 filed 4/29/85, 06/730,886 filed 4/30/85, and 06/817,853 filed 12/16/85.
Quite often the lower olefin-containing feedstocks also include minor amounts of impurities such as conjugated dienes, e.g., 1,3 butadiene, as well as allenes and acetylenes, which may be produced as a by-product of the lower olefin production process. This is particularly the case where the lower olefin is produced by pyrolysis of hydrocarbons, e.g., natural gas liquid, naphtha and gas oil, or by methane conversion, especialy methane conversion processes involving methane/solids contacting at elevated temperature to produce higher hydrocarbons (e.g., lower olefins) and coproduct water.
The presence of impurities such as conjugated dienes and the like is often detrimental to catalysts used to oligomerize lower olefins to higher hydrocarbons. Conventional diene removal steps, such as distillation, selective diene hydrogenation and the like, are costly and can cause loss of the lower olefin. Still, it would be beneficial to remove impurities from the lower olefin feedstock and/or reduce the harmful effect that these impurities have on lower olefin oligomerization catalysts.
Therefore, one object of the present invention is to provide an improved process for converting a lower olefin feedstock containing oligomerization catalyst deactivating impurities to higher hydrocarbons. Another object of the invention is to provide a process in which dienes are effectively removed from a lower olefin, diene-containing feedstock. A further object of the invention is to provide a process in which the detrimental effect on an olefin oligomerization catalyst of dienes in a lower olefin, diene-containing feed is substantially reduced.